This application relates generally to devices used by diabetics for obtaining blood samples. More particularly, the present invention provides a simple but effective vacuum device which assists in drawing blood samples from alternative puncture sites, such as the forearm, abdomen or inner thigh.
Frequent samplings of capillary blood from the fingertip is now the standard of care in the management of diabetes. Samplings may be needed as often as 8-10 times per day for control of this common metabolic disorder. The problem of fingertip discomfort has encouraged a search for alternative sites for capillary blood sampling. The underside of the forearm, the abdomen and the inner thigh are attractive sites because of their lower number of nerve endings as compared to the fingertips. Unfortunately, these alternative sites, while having fewer sensitive nerve endings, are also less likely to bleed readily when perforated by a lancet.
This well-recognized dilemma has been approached in a number of ways by various inventors and makers of equipment for diabetics. For example, attempts have been made to design a lancet device with an internal vacuum so that, immediately after causing a skin perforation, the vacuum inside the device encourages the formation of a blood drop. Many such devices are described in the patient literature. Examples are seen in U.S. Pat. Nos. 6,027,459; 5,891,053; 5,662,127; 5,666,966; 5,368,047; 4,895,147 and 4,653,513. All of the above mentioned designs are relatively complicated and therefore difficult and expensive to produce.
A simpler approach is presented in U.S. Pat. No. 5,054,499 which describes a bendable, collapsible metal dome with a skin piercing member attached to the underside of the dome. Deformation followed by reformation of the original shape of the dome is said to form a partial vacuum over the puncture site and assist in the formation of a capillary blood sample. Disadvantages of this device are the inability to see the sample, or to repeat the flexion of the metal dome if necessary, as well as the minimal amount of vacuum which can be obtained using this type of device.
Another approach is described in several patents assigned to Mercury Diagnostics (now Amira Medical). Listed U.S. Pat. Nos. of Amira are 5,867,983; 5,951,493; 5,964,718; 5,879,311 and 6,015,392. All of these patents describe devices with so-called xe2x80x9cstimulator ringsxe2x80x9d which, in various ways, surround the puncture site and, when forced down against the skin, urge the blood towards, and then out of, the skin incision. A disadvantage in all of the Amira devices is the inability to see whether an adequate blood drop has actually formed at the puncture site. Mechanically, the devices described in these Amira patents are cumbersome and expensive to manufacture.
The prior art includes various hand-held vacuum devices. For example, U.S. Pat. No. 5,871,456 provides a hand-held device vacuum device for correcting flat, inverted or retracted nipples. The device also includes a transparent tip. However, the device requires the use of two hands and does not use a spring to help generate a vacuum. Vacuum devices have also been proposed for the extraction of toxic venoms, pus or other body fluids from a skin puncture site. Goodrich in U.S. Pat. No. 5,387,203 teaches a tubular device with a plunger which is pulled upwards by the user to create an internal vacuum. Tissue is pulled into the device by the vacuum and lanced by an internal piercing member. A device specifically designed for venom extraction is taught by Andre Emerit in U.S. Pat. No. 4,287,819. In this two-chambered device, downward pressure on a plunger expels air from a lower chamber while creating a vacuum in an upper chamber. In the final moment of depression of the plunger, the two chambers are connected by an orifice in the hollow plunger, causing a vacuum over the skin. A device based on U.S. Pat. No. 4,287,819 is presently marketed by Sawyer Products of Long Beach, Calif. A disadvantage of the device is the suddenness of the vacuum application and the inability to vary its force. A related device is taught by Michel Emerit in U.S. Pat. No. 5,984,876. Neither Emerit device uses any kind of internal spring, therefore differing fundamentally from the present invention.
The invention to be described has advantages over prior devices in that it is small, simple to use and inexpensive to manufacture. A transparent tip allows easy viewing of the developing blood drop. The amount of vacuum force can be readily controlled by the user. If necessary, the vacuum can be recreated without removing the device from the skin or disturbing an already partially formed drop. These and other advantages will become apparent with further descriptions of the device.